Dynamo-electric machine



NOV. 3, 1936. F4 w MERRlLL 2,059,886

DYNAMO-ELECTRIC MACHINE Filed Feb. 14, 1936 Inventor v Frank W- MB sAttovn'eg.

55 proved excitation system, and Fig. is a par- Patented Nov. 3, 1936 iI I UNITED STATES PATENT OFFICE DYNAMO-ELECTRIC momma Frank W. Merrill,Fort Wayne, Ind., assignor to General Electric Company, a corporation ofNew York Application February 14, 1936, Serial No. 63,870

8 Claims. (Cl. 171-209) My invention relates to improvements in dynatialsectional side elevation of the machine 11- mo-electric machines andparticularly to the type lustrated in Figs. 3 and 4. of machine havinga' permanent magnet excita- Referring to the drawing, in Figs. 1 and 2,I tion system. have illustrated a, dynamo-electric machine in- 5Permanent magnets have heretofore been used eluding a stationary memberprovided with a 5 for the excitation of small dynamo-electricmalaminated core. ID of magnetic material having chines, but the size ofthese machines has gena winding ll arranged in slots 12 formed in theerally been relatively large compared to an elecmagnetic core Ill. Thestationary core I0 is trically excited machine of the same rating. Suchsecured within a frame 13 which is provided with m magnets have usuallybeen of the horseshoe shape a base 14 for supporting the dynamo-electricmato obtain the length and shielding against dechine. Thefieldexcitation system of this dymagnetization necessary forsatisfactory pername-electric machine comprises a rotatable formanceand, because of the size and shape of member which is arranged tocooperate electrothese magnets, they have usually been placed ondynamically with the stationary core 10 and the in the stator of themachine. Recent improvewinding il. This rotatable member includes two 15ments in permanent magnet materials of high ellmfe e t ally e ding thinbar-type magnetic retentivity, such as may be formed of manent magnetpads or pole pieces l5 mounted an iron-nickel-aluminum alloy, asdescribed in upon a cylindrical soft iron or soft steel core 16 UnitedStates Patent 1,947,274, February 13, 1934, secured to a shaft H. Theinner surfaces of these m Ruder, or an iron-nickel-aluminum-cobaltalloy, pole pieces extend over almost the entire ciras described inUnited States Patent 1,968,569, cumf rence of th core "5, ut theouterSurface July 13, 1934, Ruder, make possible the use of of each pole pi ehas allele re only sligh l pads or short bar-shaped permanent magnetsgreater than 120 electrical degrees. These pole which retain theirmagnetism indefinitely. pieces are prefera ly f rm d f an alloy of as Anobject of my invention is to provide a, dyminum, nickel, cobalt, andiron, referred to above. name-electric machine having an excitation sysegreatest etic energy output ro a given tem of substantially greaterlength axially of weight of permanent magnet material is the machinethan the magnetic core with which tamed h the flux e y Of s a y is aboutthe excitation system cooperates electro-dynami- 12,000 maxwells P Inthe magnetic 39 cally and an arrangement for concentrating the cuit ofan ordinary direct current motor, the iiux produced by this excitationsystem into the ux densi y in e air ap a y varies eair gap between themagnetic core a d th tween 40,000 and 60,000 maxwells per sq. 1n.citation system and for minimizing flux leakage Thus, in adynamo-electric machine provided at the ends of the excitation systembeyond the With permanent magnet pole p eces having flux air apdensityof 12,000 maxwells per sq. in., or less, pro- 5 Further objects andadvantages of my inven- Vision must be made for developing higher 3 ionwill become apparent, and my invention will nflux density than the fluxdensity within the be better understood, from the following descripipole pieces' In order to obtam t referring, the accompanying drawing andsired air gap density, I construct the pole pieces 40 the features ofnovelty which characterize m of substantmuy. greater axial. E than 40 ythe length of the stationary magnetic core l0 and invention will bepointed out with particularity f 18 hi h in the claims appended to andforming a part provide soft iron or soft steel pole aces w c of thisspecification act as flux concentrators. These pole faces of In thedrawing 1 is an end vi 1 d soft magnetic material are carried on theouter nammelectiric j havh'l a r 1 surfaces of the pole pieces andprovide a pathof with an embodime t f 0 or provided low magneticreluctance for the flux produced by n o my mPFWed excitation the portionof the pole pieces extending beyond system, Fig. 2 1s a partialsectional side elevathe air gap between the pole ieces and the ma tionof the machine illustrated in Fi 1' F1 3 p g 3 netic core II), incompleting the magnetic cir- 50 is an enjdtview of a dynamo-electricmachine havit through the stationary core I 0, thereby min- 50 2 s fggfwlth embodiment of my imizing flux leakage at the ends of the pole (Weexc a 3 4 s an end pieces l5. As shown in Figs. 1 and 2, thepole VIEW m-electric machine having a stafaces ill have substantially the sameaxial length tor provided with another embodiment of my imandsubstantially the same pole face surface area as the pole pieces 15. Inthis manner, flux densities may be obtained in the air gap which compare favorably with the air gap densities in the ordinary type of directcurrent excited dynamoelectric machine.

In the embodiments of my invention illustrated in Figs. 3, 4, and 5 thednamo-electrlc machines include a rotatable member provided with alaminated core I! of magnetic material having a winding 2|] arranged inslots 21 of the core l9 and connected to a commutator 22. This rotatablemember is essentially the usual type direct current armature and ismounted upon a shaft 23.

The excitation system of the dynamo-electric machine shown in Fig. 3comprises a stationary member arranged to cooperate electrodynamicallywith the rotatable core l9, and includes two circumferentially extendingthin bar-typ permanent magnet pads or pole pieces 24 which are welded,bolted, or otherwise secured, to a soft iron or soft steel frame 25. Theframe 25 is mounted in another frame or cylindrical shell 26 which isprovided with a. base 21 for supporting the dynamo-electric machine. Asin the embodiment illustrated in Figs. 1 and 2, the pole pieces 24 arepreferably formed of an alloy of aluminum, nickel, cobalt, and iron. Inorder to obtain the desired air gap flux density, these pole pieces 24and the frame 25 are constructed of a substantially greater axial lengththan the length of the rotatable core I9 and are provided with soft ironor soft steel pole faces 28 which act as flux concentrators orcollectors. These pole faces of soft magnetic material and substantiallythe same axial length and pole face surface area as the pole pieces 24provide a path of low magnetic reluctance for concentrating orcollecting the flux produced by the portion of the pole pieces extendingbeyond the airgap between the pole pieces and the magnetic core I9 andminimize flux leakage at the ends of these pole pieces.

In Fig. 4 I have illustrated a dynamo-electric machine which includes arotatable member of the same construction as that illustrated in Fig.

3, and is provided with an excitation system comprising a stationarymember arranged to cooperate electrodynamically with the rotatable corel9. This stationary member includes a pair of circumferentiallyextending thin bar-type permanent magnet pads or pole pieces 24 whichare preferably formed of an alloy of aluminum, nickel, cobalt, and iron,referred to above, and have a substantially greater axial length thanthe rotatable core l9. Pole faces 28, of a soft magnetic material,having substantially the same length and same pole fade surface area asthe permanent magnet pads are secured thereto, and act as fluxconcentrators or collectors for the ends of the pole pieces extendingbeyond the air gap. These pole faces are formed with beveled edges 29and the pole pieces are spaced apart and secured to a stationary frame25 of magnetic material by a pair of non-magnetic interpolar members 30provided with beveled flanges 3| arranged to cooperate with the bevelededges 29 of the pole faces 28. These interpolar members 30 are bolted,or otherwise secured, to the frame 25 and to a frame 26 formed with abase 21 for supporting the dynamo-electric machine. In this constructionthe pole pieces 24, the frame 25, and the interpolar securing members 30can all be manufactured separately of one another and provide a simplearrangement which can be readily assembled and disassembled. Thisconstruction also insures against possible slight demagnetization of thepermanent magnet pads 24 during assembly, such as might occur if thesemagnets are welded, or otherwise heated, when they are secured to theframe 25.

Modifications of the various embodiments of my invention, which I haveillustrated and described, will occur to those skilled in the art. Idesire it to be understood, therefore, that my invention is not to belimited to the particular arrangements disclosed, and I intend, in theappended claims, to cover all modifications which do not depart from thespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A dynamo-electric machine having a core of magnetic material providedwith a winding, a magnetic excitation system including a pluralityofpermanent magnet pole pieces of substantially greater axial lengththan said core arranged to cooperate electrodynamically therewith, andmeans for concentrating the flux produced by said excitation system inthe air gap between said core and said pole pieces and for minimizingflux leakage beyond the air gap.

2. A dynamo-electric machine having a core of magnetic material providedwith a winding, a magnetic excitation system including a plurality ofpermanent magnet pole pieces of substantially greater axial length thansaid core arranged to cooperate electrodynamically therewith, and meansincluding pole faces of soft magnetic Inaterial carried by said polepieces and having substantially the same axial length as said polepieces for concentrating the flux produced by said excitation system inthe, air gap between said core and said pole pieces and for minimizingflux leakage beyond the air gap.

3. A dynamo-electrical machine having a core of magnetic materialprovided with a winding, a magnetic excitation system arranged tocooperate electrodynamically with said core including circumferentiallyextending thin permanent magnet pole pieces of substantially greateraxial length than said core, and pole faces of soft magnetic materialcarried by said pole pieces and having substantially the same axiallength as said pole pieces.

4. A dynamo-electric machine having a core of magnetic material providedwith a winding, a magnetic excitation system arranged to cooperateelectrodynamlcaily with said core including a sec-- and core of magneticmaterial of substantially greater axial length than said first mentionedcore, permanent magnet pole pieces secured to said second core, and polefaces of soft magnetic material carried by said pole pieces, said polepieces and pole faces having substantially the same axial length as saidsecond core.

5. A dynamo-electric machine having a core of magnetic material providedwith a winding, a magnetic excitation system arranged to cooperateelectrodynamicaliy with said core including circumferentially extendingthin permanent magnet pole pieces of an alloy of high magneticretentivity, each of said pole pieces having an axial lengthsubstantially greater than said core, and pole faces of soft magneticmaterial carried by "said pole pieces and having substantially the sameaxial length as said pole pieces.

6. An excitation system for a dynamo-electric machine including a coreof magnetic material.

circumferentially extending thin permanent magnet pole pieces secured tosaid core, and pole faces of soft magnetic material carried by said polepieces, said pole faces having substantially the same axial length assaid pole pieces and having substantially the same pole face surfacearea as said pole pieces.

7. An excitation system for a dynamo-electric machine including a frameofmagnetic material, permanent magnet pole pieces, pole faces of softmagnetic material carried by said pole pieces and having substantiallythe same axial length as said pole pieces, and means including a memberof non-magnetic material secured to said frame for spacing apart and forsecuring said pole pieces to said frame.

8. A dynamo-electric machine having a core of magnetic material providedwith a winding, a magnetic excitation system arranged to cooperateelectrodynamically with said core including a second core of magneticmaterial of substantially greater axial length than said first mentionedcore member, permanent magnet pole pieces secured to said second core,pole faces of soft magnetic material secured to said permanent magnetpole pieces, said pole pieces and said pole faces having substantiallythe same length as said second core, and means including a member ofnonmagnetic material secured to said second magnetic core for spacingapart and for securing said pole pieces to said second magnetic core.

FRANK w. MERRILL.

